From the prior art, DC-DC converters with a converter circuit and a controller are known, where the controller produces a drive signal for operating the switched mode operation of the converter circuit. By means of the controller, it is possible to adapt the converter circuit to the operating conditions of the DC-DC converter, in particular to the load of the DC-DC converter. A disadvantage of such a DC-DC converters is that the converter circuit has a low efficiency when there is little load to the DC-DC converter circuit.
A multiphase DC-DC converter is known from the document DE 11 2008 004 030 T5. This DC-DC converter consists of a number of converter circuits that are switched parallel to each other. The amount of converter circuits that are in operation can be changed, whereby each one of the operating converter circuits performs one switching mode operation. The DC-DC converter consists of a controller that produces a number of drive signals for the converter circuits which have different phases, in order to drive the control elements of the respective converter circuits, by means of which the switch mode operation processes can be controlled. Each converter circuit is permanently assigned to one phase. Depending on the operating conditions of the DC-DC converter, the controller determines the amount of converter circuits that are to be operated. Thus, based on the operating conditions, converter circuits of the DC-DC converter are switched off, which means that no drive signals are produced which have the phase that is assigned to these converter circuits.
The multiphase DC-DC converter that is known from the document DE 11 2008 004 030 T5 can be adapted to the load of the DC-DC converter. This is advantageous, since it is possible to operate the converter circuit of the multiphase DC-DC converter with different loads to the multiphase DC-DC converter in such a way, that it can be operated with a good efficiency. Yet, a disadvantage of the multiphase DC-DC converter is that the electromagnetic noise emission increases as soon as one or more phases are inactive, which means when not all converter circuits are operated. Input and output filters must be elaborately designed for the frequencies of a phase and at times also for sub-harmonic noise.
A multiphase DC-DC converter is also known from the document DE 10 2009 054 957 A1. This DC-DC converter consists of a number of converter circuits that are switched parallel to each other. The amount of converter circuits that are to be operated can be changed. The DC-DC converter consists of a controller that produces a number of drive signals for the converter circuits which consist of different phases in relation to each other, in order to drive the control elements of the respective converter circuits, by means of which the switch mode operation processes can be controlled. Depending on an operating condition of the DC-DC converter, the controller determines the amount of converter circuits that have to be operated, and determines the phase difference between the drive signals, if the controller determines that the number of converter units, that have to be operated should be two or more. By means of this multiphase DC-DC converter, power can be transmitted within a wide range with high efficiency. Yet, when there is less load, the amount of phases is reduced, which leads to an increase in ripples.